1. Field of the Invention
The present invention relates to an epoxy resin composition for semiconductor encapsulation. In particular, the present invention relates to an epoxy resin composition for semiconductor encapsulation exhibiting good flowability and excellent curing properties.
2. Description of the Related Art
Recent developments in high-density and automatic technology for mounting semiconductor packages on printed boards have induced surface mounting techniques, where semiconductor packages may be directly soldered onto a surface of a printed board instead of being attached thereto by lead pins. Such mounting techniques have triggered the use of flat plastic packages (FPPs) suitable for high-density and surface mounting instead of conventional dual inline packages (DIPs). The flat plastic packages may have an increased size and number of pins due to improved microprocessing technology, i.e., improved integration of semiconductors. Conventional surface mounting techniques may require enhanced moldability of semiconductor packages in order to reduce the occurrence of molding defects, e.g., incomplete filling of the packages, formation of voids, and so forth, during packaging in order to increase productivity. A conventional semiconductor molding technique may include use of epoxy resins.
Epoxy resins may be utilized in various applications, including adhesives and electrically insulating materials, due to their high heat and moisture resistance, excellent electrical properties and good adhesiveness. Particularly, epoxy resins may be useful in molding electronic circuit components, e.g., semiconductors. Semiconductors may be molded by hermetic molding techniques, e.g., using metals and ceramics, and resin molding techniques, e.g., using phenol, silicone and epoxy resins. Conventional resin molding techniques using epoxy resins may be the most suitable in terms of economic efficiency, productivity and physical properties. In particular, a conventional semiconductor molding technique may include forming an epoxy resin molding material into a tablet and, subsequently, molding the semiconductor with the tablet via a low-pressure transfer molding machine.
Conventional epoxy resin molding materials may be at a B-stage state, i.e., a material in a half-cured state that may be kept at room temperature for several days or stored at low temperature for a long period of time to complete curing. However, such curing of B-stage epoxy resin molding material may result in poor moldability due to a difference in thermal hysteresis between the surface and the inside of the epoxy resin material at relatively low temperatures. In particular, use of such epoxy resin molding materials in semiconductor molding may trigger outer defects, e.g., incomplete filling, voids, pinholes, and so forth, and internal defects, e.g., deformation of gold lines, internal voids, and so forth, and, thereby, reduce semiconductor reliability, e.g., decrease moisture resistance reliability and minimized soldering heat resistance.
In an attempt to improve molding properties of epoxy resin materials, curing accelerators have been suggested to improve moldability of epoxy resin materials for semiconductor encapsulation without deterioration in production efficiency.
Additionally, high degree inorganic fillers have been suggested for use in epoxy resin materials to improve the density and heat and moisture resistance of the semiconductor devices. Accordingly, low-viscosity epoxy resins, e.g., biphenyl type epoxy resins, and self-extinguishable resins, i.e., environmentally friendly epoxy resin compositions, may be used instead of novolac type epoxy resins and phenolic resins. However, such biphenyl epoxy resins and self-extinguishable resins may be less reactive than novolac type epoxy resins and phenolic resins. Reduced reactivity may cause incomplete curing reactions when conventional curing accelerators are used, thereby triggering deterioration of semiconductor moldability, curing properties and storage stability.
Accordingly, there is a need for a new epoxy resin composition capable of exhibiting high reactivity and good storage stability, while maintaining good molding properties, density, and heat and moisture resistance of a semiconductor device.